In the context of climate change, the study of the variability of the climatic extremes in several regions of the world is of capital importance. This study has as main objective to analyze the variability of extreme ...In the context of climate change, the study of the variability of the climatic extremes in several regions of the world is of capital importance. This study has as main objective to analyze the variability of extreme temperature events in the Beninese basin of the Niger River for the recent and the near future. To achieve this objective, seven (07) extreme temperature indices based on historical daily temperature observations (1976 to 2019) and REMO RCM simulation outputs of RCP4.5 and RCP8.5 scenarios (2021-2050) were calculated. The obtained results were represented by calculating the means for each index and analyzing the trends and their significance by the Mann-Kendall method. The results show that the indices of extreme temperature intensity (TNn, TXx, and DTR), and those related to the frequency of warm sequences (WSDI, TN90p and TX90p) have experienced a significant increase in the past. This increase will continue until 2050. In contrast, the cold sequence frequency index (CSDI) decrease over the historical period as well as over the future period. These indices show much more change with the RCP8.5 scenario than with the RCP4.5 of the REMO climate model. Only the TXx and CSDI indices show statistically significant changes at all stations.展开更多
In the context of a changing climate,the Beninese Niger River basin has been the focus of several research studies for the quantification,planning,and modeling of water and related resources for sustainable use.This r...In the context of a changing climate,the Beninese Niger River basin has been the focus of several research studies for the quantification,planning,and modeling of water and related resources for sustainable use.This research aims to characterize the historical(1976-2019)and projected(2021-2050)hydrological drought of the Beninese Niger River basin.The study used daily observations of rainfall,maximum and minimum temperatures,runoff rates and simulations of HIRHAM and REMO RCMs from fifteen(15)rainfall stations installed around the basin.It uses standardized streamflow indices(SDI)at 12-month and 36-month time steps.The results show that the calculated SDI indices show,on average,for all the model scenarios used,chronological trends of increase.These increases are not significant(are of the order of 0.00001 per year).The analysis of the SDI indices shows that,on average,the hydrological droughts in the Beninese basin of the Niger River will increase at 36 months and decrease at 12 months of the SDI.In fact,these small variations of hydrological droughts will be accompanied by the increase of their duration and the decrease of their magnitudes.The droughts detected in the Benin basin of the Niger River during the historical period will continue until 2050 in the same range but with more extended drought lengths.It should be noted that most of the changes observed in the calculated and analyzed indices are not significant.展开更多
Using 70 years of daily rainfall records in eight stations, an analysis of variability and trends of daily heavy rainfall events over Niger River Basin Development Authority Area was carried out by using Standardized ...Using 70 years of daily rainfall records in eight stations, an analysis of variability and trends of daily heavy rainfall events over Niger River Basin Development Authority Area was carried out by using Standardized Anomaly Index and Spearman Rank Correlation Coefficient. Significant temporal variability on interannual and decadal time-scales was observed in the frequency of heavy rainfall events and annual heavy rainfall amount. Both the annual heavy rainfall amount and frequency of heavy rainfall events demonstrated no pronounced temporal decreasing or increasing trend. However, more recent data records from 1981 onwards revealed an increasing trend. Thus, evidence of a temporal change is apparent in heavy rainfall events in the last three decades in sympathy with global warming.展开更多
The study investigates the trends in temperature in the Upper and Lower Niger Basin Development Authority Areas using standardized Anomaly Index, Gaussian Low Pass and Spearman’s correlation coefficient. From the dat...The study investigates the trends in temperature in the Upper and Lower Niger Basin Development Authority Areas using standardized Anomaly Index, Gaussian Low Pass and Spearman’s correlation coefficient. From the data collected and analyzed, the mean annual temperature and mean annual maximum temperature demonstrated pronounced temporal increasing trend in the period 1951-2010 while the mean annual minimum temperature showed no trend. The rate of increase in mean annual temperature, mean annual maximum and minimum temperatures was 0.45°C, 0.40°C and 0.20°C respectively. The mean annual maximum temperature warmed faster than the mean annual minimum leading to increase in diurnal range of temperature. The annual temperature anomaly in the study area tracks the observed anomalies for the Northern Hemisphere in the 20th century. The decadal temperature increase is very small particularly as from 1980.展开更多
The river Niger is the 3rd longest river in Africa, with a stream length of 4200 km, a drainage basin of 2,170,500 km2 of which 1,500,000 km2 is an active basin, and an average discharge of about 6000 m3/s. The natura...The river Niger is the 3rd longest river in Africa, with a stream length of 4200 km, a drainage basin of 2,170,500 km2 of which 1,500,000 km2 is an active basin, and an average discharge of about 6000 m3/s. The natural variability of its rainfall and discharge is analyzed for several major sub-basins, in the context of the West African drought which has lasted for nearly 40 years, showing two paradoxes: the increase of Sahelian runoff since the beginning of the drought due to land degradation, and the steep decrease of sudanian runoff over the same period, substantiated by the long-lasting decrease of the groundwater tables. Much information about the water resources available in the basin is collected and analysed by the NBA1, which is summarized in this paper including surface water resources, rainfall over the basin, existing and projected dams. The river Niger is deficient in dams to control water, especially in its upper and middle basins. Nigeria has many dams, including large dams, while Burkina Faso has many small dams, but there are only a few dams upstream of the river Niger in Mali/Guinea/Ivory Coast. It is therefore likely that several dams will be built in the Niger basin in the coming years, and several are in the project phase. All of these will have a large impact on the river Niger regime and the environment, especially the Fomi dam which will change significantly the river regime upstream of the inner Delta, inducing an important reduction of the flooded area, and the Tossaye dam on the Saharan border of Mali which could promote a very significant level of evaporation. It is very important before building these dams to take into account the past years variability of climate and river regime.展开更多
Population growth and increasing needs make our current societies a considerable source of environmental threats. Going towards sustainable cities where harmony exists between economic, socio-cultural and environmenta...Population growth and increasing needs make our current societies a considerable source of environmental threats. Going towards sustainable cities where harmony exists between economic, socio-cultural and environmental issues is a necessity that is essential if we want to bequeath a livable world to future generations. Cities produce huge quantities of domestic and industrial waste, the management of which is becoming a growing problem for city managers. Located on the banks of the Niger River, the city of Niamey, capital of the Republic of Niger, is supplied with drinking water from this river. Significant quantities of sludge are produced by the plant following the treatment of this water. This study focuses on the physico-chemical characterization of this sludge which is now directly discharged into the Niger River. A total of 12 samples of pasty sludge taken from the pre-settling ponds were analyzed. The samples were previously dried, crushed, sieved and packaged. Physical (pH, EC and particle size), chemical (Ca, Mg, Na, K, CEC, AE, P, C, MO and N) and metallic trace elements (Pb, Ni, Cu, Zn, Cd, Mn) parameters and Al) were analyzed in the laboratory. The results show that the sludge is weakly acidic (pH between 4.16 and 5.71), conductive (<0.35 mS/cm) and rich in fine elements (12.1% to 77.71% clay). The nutrient content is low in nitrogen (<0.25%), phosphorus (<2.5 ppm), potassium (between 1 to 188 Mèq/100g) and organic matter (less than 2.88%). The concentrations of ETM comply with the values admissible in residual materials (French decree of 08/01/1998). This sludge can be recovered, especially in agriculture.展开更多
Water resources assessment in poorly gauged and ungauged basins demand supportive rainfall-runoff estimation, while resolving practical water resource management and planning issues. In this study, the research method...Water resources assessment in poorly gauged and ungauged basins demand supportive rainfall-runoff estimation, while resolving practical water resource management and planning issues. In this study, the research method employed involves rainfall-runoff modeling and simulation with proper efficiency criteria evaluation using the MODMENS modeling platform, a numerical rainfall-runoff semi-distributed GR2M conceptual lumped model. The rainfall-runoff simulation was carried-out in three selected sub-basins of Lower River Niger Basin based on observable discharge dataset. Related error estimation was carried-out to estimate the runoff simulation uncertainty while model optimization approach entails use of Rosenbrock-Simplex method and model reliability evaluation entails the use of Nash and Sutcliffe efficiency criteria methods. Result shows a satisfactory model performance at Baro and Makurdi gauging stations （savannah ecological zone） while under-estimation characterizes simulated flow at Onitsha gauging station（Forest ecological region）. Seasonally, the model best fit the dry season flow but underestimate during the high flow periods （rainy seasons and wetter years）.展开更多
文摘In the context of climate change, the study of the variability of the climatic extremes in several regions of the world is of capital importance. This study has as main objective to analyze the variability of extreme temperature events in the Beninese basin of the Niger River for the recent and the near future. To achieve this objective, seven (07) extreme temperature indices based on historical daily temperature observations (1976 to 2019) and REMO RCM simulation outputs of RCP4.5 and RCP8.5 scenarios (2021-2050) were calculated. The obtained results were represented by calculating the means for each index and analyzing the trends and their significance by the Mann-Kendall method. The results show that the indices of extreme temperature intensity (TNn, TXx, and DTR), and those related to the frequency of warm sequences (WSDI, TN90p and TX90p) have experienced a significant increase in the past. This increase will continue until 2050. In contrast, the cold sequence frequency index (CSDI) decrease over the historical period as well as over the future period. These indices show much more change with the RCP8.5 scenario than with the RCP4.5 of the REMO climate model. Only the TXx and CSDI indices show statistically significant changes at all stations.
文摘In the context of a changing climate,the Beninese Niger River basin has been the focus of several research studies for the quantification,planning,and modeling of water and related resources for sustainable use.This research aims to characterize the historical(1976-2019)and projected(2021-2050)hydrological drought of the Beninese Niger River basin.The study used daily observations of rainfall,maximum and minimum temperatures,runoff rates and simulations of HIRHAM and REMO RCMs from fifteen(15)rainfall stations installed around the basin.It uses standardized streamflow indices(SDI)at 12-month and 36-month time steps.The results show that the calculated SDI indices show,on average,for all the model scenarios used,chronological trends of increase.These increases are not significant(are of the order of 0.00001 per year).The analysis of the SDI indices shows that,on average,the hydrological droughts in the Beninese basin of the Niger River will increase at 36 months and decrease at 12 months of the SDI.In fact,these small variations of hydrological droughts will be accompanied by the increase of their duration and the decrease of their magnitudes.The droughts detected in the Benin basin of the Niger River during the historical period will continue until 2050 in the same range but with more extended drought lengths.It should be noted that most of the changes observed in the calculated and analyzed indices are not significant.
文摘Using 70 years of daily rainfall records in eight stations, an analysis of variability and trends of daily heavy rainfall events over Niger River Basin Development Authority Area was carried out by using Standardized Anomaly Index and Spearman Rank Correlation Coefficient. Significant temporal variability on interannual and decadal time-scales was observed in the frequency of heavy rainfall events and annual heavy rainfall amount. Both the annual heavy rainfall amount and frequency of heavy rainfall events demonstrated no pronounced temporal decreasing or increasing trend. However, more recent data records from 1981 onwards revealed an increasing trend. Thus, evidence of a temporal change is apparent in heavy rainfall events in the last three decades in sympathy with global warming.
文摘The study investigates the trends in temperature in the Upper and Lower Niger Basin Development Authority Areas using standardized Anomaly Index, Gaussian Low Pass and Spearman’s correlation coefficient. From the data collected and analyzed, the mean annual temperature and mean annual maximum temperature demonstrated pronounced temporal increasing trend in the period 1951-2010 while the mean annual minimum temperature showed no trend. The rate of increase in mean annual temperature, mean annual maximum and minimum temperatures was 0.45°C, 0.40°C and 0.20°C respectively. The mean annual maximum temperature warmed faster than the mean annual minimum leading to increase in diurnal range of temperature. The annual temperature anomaly in the study area tracks the observed anomalies for the Northern Hemisphere in the 20th century. The decadal temperature increase is very small particularly as from 1980.
文摘The river Niger is the 3rd longest river in Africa, with a stream length of 4200 km, a drainage basin of 2,170,500 km2 of which 1,500,000 km2 is an active basin, and an average discharge of about 6000 m3/s. The natural variability of its rainfall and discharge is analyzed for several major sub-basins, in the context of the West African drought which has lasted for nearly 40 years, showing two paradoxes: the increase of Sahelian runoff since the beginning of the drought due to land degradation, and the steep decrease of sudanian runoff over the same period, substantiated by the long-lasting decrease of the groundwater tables. Much information about the water resources available in the basin is collected and analysed by the NBA1, which is summarized in this paper including surface water resources, rainfall over the basin, existing and projected dams. The river Niger is deficient in dams to control water, especially in its upper and middle basins. Nigeria has many dams, including large dams, while Burkina Faso has many small dams, but there are only a few dams upstream of the river Niger in Mali/Guinea/Ivory Coast. It is therefore likely that several dams will be built in the Niger basin in the coming years, and several are in the project phase. All of these will have a large impact on the river Niger regime and the environment, especially the Fomi dam which will change significantly the river regime upstream of the inner Delta, inducing an important reduction of the flooded area, and the Tossaye dam on the Saharan border of Mali which could promote a very significant level of evaporation. It is very important before building these dams to take into account the past years variability of climate and river regime.
文摘Population growth and increasing needs make our current societies a considerable source of environmental threats. Going towards sustainable cities where harmony exists between economic, socio-cultural and environmental issues is a necessity that is essential if we want to bequeath a livable world to future generations. Cities produce huge quantities of domestic and industrial waste, the management of which is becoming a growing problem for city managers. Located on the banks of the Niger River, the city of Niamey, capital of the Republic of Niger, is supplied with drinking water from this river. Significant quantities of sludge are produced by the plant following the treatment of this water. This study focuses on the physico-chemical characterization of this sludge which is now directly discharged into the Niger River. A total of 12 samples of pasty sludge taken from the pre-settling ponds were analyzed. The samples were previously dried, crushed, sieved and packaged. Physical (pH, EC and particle size), chemical (Ca, Mg, Na, K, CEC, AE, P, C, MO and N) and metallic trace elements (Pb, Ni, Cu, Zn, Cd, Mn) parameters and Al) were analyzed in the laboratory. The results show that the sludge is weakly acidic (pH between 4.16 and 5.71), conductive (<0.35 mS/cm) and rich in fine elements (12.1% to 77.71% clay). The nutrient content is low in nitrogen (<0.25%), phosphorus (<2.5 ppm), potassium (between 1 to 188 Mèq/100g) and organic matter (less than 2.88%). The concentrations of ETM comply with the values admissible in residual materials (French decree of 08/01/1998). This sludge can be recovered, especially in agriculture.
文摘Water resources assessment in poorly gauged and ungauged basins demand supportive rainfall-runoff estimation, while resolving practical water resource management and planning issues. In this study, the research method employed involves rainfall-runoff modeling and simulation with proper efficiency criteria evaluation using the MODMENS modeling platform, a numerical rainfall-runoff semi-distributed GR2M conceptual lumped model. The rainfall-runoff simulation was carried-out in three selected sub-basins of Lower River Niger Basin based on observable discharge dataset. Related error estimation was carried-out to estimate the runoff simulation uncertainty while model optimization approach entails use of Rosenbrock-Simplex method and model reliability evaluation entails the use of Nash and Sutcliffe efficiency criteria methods. Result shows a satisfactory model performance at Baro and Makurdi gauging stations （savannah ecological zone） while under-estimation characterizes simulated flow at Onitsha gauging station（Forest ecological region）. Seasonally, the model best fit the dry season flow but underestimate during the high flow periods （rainy seasons and wetter years）.
